Field
The present invention primarily relates to a process for producing certain phosphorus-containing cyanohydrin esters of hereinbelow-defined formula (I) and the use thereof for producing glufosinate/glufosinate salts. The present invention further relates to a process for producing glufosinate/glufosinate salts.
Description of Related Art
Phosphorus-containing cyanohydrin esters are valuable intermediates in various industrial fields, in particular for producing biologically active substances which can be employed in the pharmaceutical/agrochemical sector.
U.S. Pat. No. 4,168,963 describes a wide variety of phosphorus-containing herbicidally active compounds, among which in particular phosphinothricin (2-amino-4-[hydroxy(methyl)phosphinoyl]butanoic acid; common name: glufosinate, referred to hereinbelow as glufosinate) and the salts thereof have attained commercial importance in the agrochemical sector.

Methods for producing intermediates for the synthesis of such phosphorus-containing herbicidally active compounds, in particular of glufosinate, are described in U.S. Pat. Nos. 4,521,348, 4,599,207 and 6,359,162B1 for example.
Reactions of cyanohydrin esters and methanephosphonous esters are described in U.S. Pat. Nos. 4,521,348 or 4,599,207 for example.
While the prior art processes for producing phosphorus-containing cyanohydrin esters allow production of the desired phosphorus-containing cyanohydrin esters, in some cases in very good yield, they do still have disadvantages such as, for example, yields of phosphorus-containing cyanohydrin esters that are still in need of improvement, an excessively high proportion of coupling products or byproducts, excessively complex purification/isolation of the phosphorus-containing cyanohydrin esters and/or reaction conditions that are excessively arduous in terms of process/plant engineering.